1. Field
Embodiments of the invention relate to a thin film transistor, and more particularly, to a thin film transistor capable of low-voltage driving and a display device including the thin film transistor.
2. Description of the Related Art
Display devices are classified into types including liquid crystal display (“LCD”) devices, organic light emitting diode (“OLED”) display devices, plasma display panel (“PDP”) devices, electrophoretic display (“EPD”) devices, and the like, based on a light emitting scheme thereof.
A thin film transistor (“TFT”) used in an LCD device or an OLED device is used as a switching element for controlling operation of each pixel and a driving element for driving a pixel. In this instance, the thin film transistor serves as an ON/OFF switch that allows or blocks a transmission of charge or power to a pixel electrode.
In general, such a thin film transistor includes a source region and a drain region doped with high-concentration impurities, an active layer having a channel region formed between the source region and the drain region, a gate electrode insulated from the active layer to be disposed in an area corresponding to the channel region, and a source electrode and a drain electrode contacting the source region and the drain region respectively.
The active layer includes a semiconductor material such as amorphous silicon (“a-Si”) or polycrystalline silicon (polysilicon). In a case of the active layer being formed of amorphous silicon, carrier mobility therein is relatively low and thus a high-speed driving circuit may be difficult to be provided. In a case of the active layer being formed of polycrystalline silicon, carrier mobility therein is relatively high while a threshold voltage is non-uniform.
In recent times, research on the use of an oxide semiconductor as an active layer is being conducted in earnest. An oxide thin film transistor in which an oxide semiconductor is used as an active layer may be manufactured in a low-temperature process. In addition, due to having an amorphous shape, such an oxide thin film transistor may be convenient to be provided as a large-area oxide thin film transistor and may have an excellent electric characteristic, similarly to polycrystalline silicon.
It is to be understood that this background of the technology section is intended to provide useful background for understanding the technology and as such disclosed herein, the technology background section may include ideas, concepts or recognitions that were not part of what was known or appreciated by those skilled in the pertinent art prior to a corresponding effective filing date of subject matter disclosed herein.